A common method used to detect and identify biological substances suspended in air in the form of aerosols or clouds involves air sample collection in the field and their subsequent analysis in mobile laboratories. While this approach can be acceptably accurate, it has many disadvantages. Among these disadvantages includes being dangerous to personnel conducting the tests as they are exposed to hazardous biological agents. In addition, transporting the test equipment to the testing site can be difficult, especially if the test site is remote and/or in harsh terrain. Furthermore, the testing can be time-consuming in order to test large areas, thus decreasing the value of the testing by delaying obtaining the test results.
An alternative method for the remote sensing of biological substances, for example, would be a standoff detection such as a LIDAR (light detection and ranging) using an UV laser source. LIDAR technology employs laser pulses to determine the distance to an object or surface, for example. Backscattered fluorescence signals from the laser pulses encountering objects or materials indicate the presence and the location of any potential microscopic biological materials. The characteristic spectral information may also enable identification of these potential microscopic biological materials. However, there are still problems associated with this method. Employing a LIDAR system causes many molecules of interest to be directly excited by radiation in the vacuum ultraviolet (VUV) region, which, unfortunately, is heavily absorbed by the Earth's atmosphere for wavelengths below 300 mm. Thus, the LIDAR system limits the UV LIDAR detection range to only a few hundred meters, especially in high ozone urban environment.